Overview
I am a Research Fellow in the School of Social Science at Cardiff University, specialising in quantitative research on homelessness and housing insecurity. I conduct fundamental research into the causes, consequences, and outcomes of people experiencing homelessness and housing insecurity. My research also includes studies that use administrative and linked data to evaluate the effectiveness of interventions for people experiencing homelessness, including applied work such as the PHaCT randomised control trial for people leaving prison and the Upstream Cymru youth homelessness prevention intervention.
In my current role, I lead the housing and homelessness thematic research area within Administrative Data Research Wales, shaping research priorities and conducting policy and practice-relevant research. I also chair the Wales Housing and Homelessness Research Network, based at the Wales Institute of Social and Economic Research and Data (WISERD), which aims to strengthen collaboration across academic disciplines, and between academia, policy, and practice.
Publication
2026
- Williams, A. D. N. et al. 2026. Critical time intervention to prevent homelessness and improve health for people leaving prison: the PHaCT pilot RCT. Public Health Research 14 (15)(10.3310/GJJL2910)
2025
- Williams, A. D. N. et al. 2025. Critical time intervention for people leaving prison at risk of homelessness in England and Wales (PHaCT trial): a pilot feasibility randomised controlled trial.. BMJ Open 15 (12) e097753. (10.1136/bmjopen-2024-097753)
- Williams, A. D. N. et al. 2025. A pilot randomised controlled trial of a critical time intervention for people leaving prison: findings from an integrated process evaluation. BMJ Open 15 (12) e097761. (10.1136/bmjopen-2024-097761)
2024
- Thomas, I. 2024. Quantifying the association between family homelessness and school absence in Wales, UK. International Journal on Homelessness 4 (1), pp.39-55. (10.5206/ijoh.2023.3.15382)
- England, E. et al. 2024. A typology of multiple exclusion homelessness. Housing Studies 39 (3), pp.695-719. (10.1080/02673037.2022.2077917)
2023
- Thomas, I. and Mackie, P. 2023. Using administrative data linkage to drive homelessness policy: Experiences from Wales, UK. Cityscape 26 (1), pp.117-125.
- Thomas, I. and Mackie, P. 2023. Assessing the coverage and timeliness of coronavirus vaccination among people experiencing homelessness in Wales, UK: a population-level data-linkage study. BMC Public Health 23 (1) 1494. (10.1186/s12889-023-16432-x)
- Weightman, A. L. et al. 2023. Exploring the effect of case management in homelessness per components: A systematic review of effectiveness and implementation, with meta‐analysis and thematic synthesis. Campbell Systematic Reviews 19 (2) e1329. (10.1002/cl2.1329)
2022
- Trubey, R. et al., 2022. Linkage of people experiencing homeless using two consent models. International Journal of Population Data Science 7 (3)(10.23889/ijpds.v7i3.1865)
- Weightman, A. L. et al. 2022. PROTOCOL: Exploring the effect of case management in homelessness per components: A systematic review of effectiveness and implementation, with meta-analysis and thematic synthesis. Campbell Systematic Reviews 18 (1) e1220. (10.1002/cl2.1220)
2021
- Thomas, I. and Tweed, E. 2021. The promises and pitfalls of administrative data linkage for tackling homelessness. European Journal of Homelessness 15 (3), pp.177-188.
- Thomas, I. and MacKie, P. 2021. A population level study of SARS-CoV-2 prevalence amongst people experiencing homelessness in Wales, UK. International Journal of Population Data Science 5 (4) 1695. (10.23889/ijpds.v5i4.1695)
- Thomas, I. and Mackie, P. 2021. Using data linkage to improve estimates of homelessness.
2020
- Mackie, P. and Thomas, I. 2020. Exploratory analysis of education outcomes of children and young people living in homeless households. Project Report.[Online].Welsh Government. Available at: https://gov.wales/exploratory-analysis-education-outcomes-children-and-young-people-living-homeless-households-html.
- Mackie, P. and Thomas, I. 2020. Ageing and homelessness: Is there an ageing crisis for statutory homelessness services in the UK?. Project Report.[Online].ADR Wales. Available at: https://www.adruk.org/fileadmin/uploads/adruk/Documents/Data_Insights_Ageing_and_Homelessness_July_2002.pdf.
- Mackie, P. and Thomas, I. 2020. Measuring repeat homelessness. Project Report.[Online].ADR Wales. Available at: https://www.adruk.org/fileadmin/uploads/adruk/Documents/Data-Insights-Measuring-Repeat-Homelessness.pdf.
- Thomas, I. and MacKie, P. 2020. The principles of an ideal homelessness administrative data system: lessons from global practice. European Journal of Homelessness 14 (3), pp.63-85.
2017
- MacKie, P. K. , Thomas, I. and Bibbings, J. 2017. Homelessness prevention: Reflecting on a year of pioneering Welsh legislation in practice. European Journal of Homelessness 11 (1), pp.81-107.
2016
- Thomas, I. R. 2016. Network-assemblages of mediated sex: a post human study of the digital sexual practices of men who have sex with men. PhD Thesis , Cardiff University.
2014
- Clapham, D. et al., 2014. The housing pathways of young people in the UK. Environment and Planning A 46 (8), pp.2016-2031. (10.1068/a46273)
- MacKie, P. and Thomas, I. 2014. Nations apart? Experiences of single homeless people across Great Britain. Project Report.[Online].London: Crisis. Available at: http://www.crisis.org.uk/data/files/publications/NationsApart.pdf.
2012
- Clapham, D. F. et al. 2012. Housing options and solutions for young people in 2020. Project Report.York: Joseph Rowntree Foundation.
- MacKie, P. K. et al. 2012. Assessing the impacts of proposed changes to homelessness legislation in Wales: a report to inform the review of homelessness legislation in Wales. Technical Report.
- MacKie, P. K. , Thomas, I. and Hodgson, K. 2012. Impact analysis of homelessness legislation in Wales: A report to inform the review of homelessness legislation in Wales. Project Report.[Online].Cardiff: Welsh Assembly Government. Available at: http://www.senedd.assemblywales.org/documents/s7352/Impact%20analysis%20of%20existing%20homelessness%20legislation%20in%20Wales.pdf.
2010
- Clapham, D. F. et al. 2010. Young people and housing in 2020: identifying key drivers for change. Project Report.York: Joseph Rowntree Foundation.
Articles
- Williams, A. D. N. et al. 2026. Critical time intervention to prevent homelessness and improve health for people leaving prison: the PHaCT pilot RCT. Public Health Research 14 (15)(10.3310/GJJL2910)
- Williams, A. D. N. et al. 2025. Critical time intervention for people leaving prison at risk of homelessness in England and Wales (PHaCT trial): a pilot feasibility randomised controlled trial.. BMJ Open 15 (12) e097753. (10.1136/bmjopen-2024-097753)
- Williams, A. D. N. et al. 2025. A pilot randomised controlled trial of a critical time intervention for people leaving prison: findings from an integrated process evaluation. BMJ Open 15 (12) e097761. (10.1136/bmjopen-2024-097761)
- Thomas, I. 2024. Quantifying the association between family homelessness and school absence in Wales, UK. International Journal on Homelessness 4 (1), pp.39-55. (10.5206/ijoh.2023.3.15382)
- England, E. et al. 2024. A typology of multiple exclusion homelessness. Housing Studies 39 (3), pp.695-719. (10.1080/02673037.2022.2077917)
- Thomas, I. and Mackie, P. 2023. Using administrative data linkage to drive homelessness policy: Experiences from Wales, UK. Cityscape 26 (1), pp.117-125.
- Thomas, I. and Mackie, P. 2023. Assessing the coverage and timeliness of coronavirus vaccination among people experiencing homelessness in Wales, UK: a population-level data-linkage study. BMC Public Health 23 (1) 1494. (10.1186/s12889-023-16432-x)
- Weightman, A. L. et al. 2023. Exploring the effect of case management in homelessness per components: A systematic review of effectiveness and implementation, with meta‐analysis and thematic synthesis. Campbell Systematic Reviews 19 (2) e1329. (10.1002/cl2.1329)
- Trubey, R. et al., 2022. Linkage of people experiencing homeless using two consent models. International Journal of Population Data Science 7 (3)(10.23889/ijpds.v7i3.1865)
- Weightman, A. L. et al. 2022. PROTOCOL: Exploring the effect of case management in homelessness per components: A systematic review of effectiveness and implementation, with meta-analysis and thematic synthesis. Campbell Systematic Reviews 18 (1) e1220. (10.1002/cl2.1220)
- Thomas, I. and Tweed, E. 2021. The promises and pitfalls of administrative data linkage for tackling homelessness. European Journal of Homelessness 15 (3), pp.177-188.
- Thomas, I. and MacKie, P. 2021. A population level study of SARS-CoV-2 prevalence amongst people experiencing homelessness in Wales, UK. International Journal of Population Data Science 5 (4) 1695. (10.23889/ijpds.v5i4.1695)
- Thomas, I. and MacKie, P. 2020. The principles of an ideal homelessness administrative data system: lessons from global practice. European Journal of Homelessness 14 (3), pp.63-85.
- MacKie, P. K. , Thomas, I. and Bibbings, J. 2017. Homelessness prevention: Reflecting on a year of pioneering Welsh legislation in practice. European Journal of Homelessness 11 (1), pp.81-107.
- Clapham, D. et al., 2014. The housing pathways of young people in the UK. Environment and Planning A 46 (8), pp.2016-2031. (10.1068/a46273)
Monographs
- Thomas, I. and Mackie, P. 2021. Using data linkage to improve estimates of homelessness.
- Mackie, P. and Thomas, I. 2020. Exploratory analysis of education outcomes of children and young people living in homeless households. Project Report.[Online].Welsh Government. Available at: https://gov.wales/exploratory-analysis-education-outcomes-children-and-young-people-living-homeless-households-html.
- Mackie, P. and Thomas, I. 2020. Ageing and homelessness: Is there an ageing crisis for statutory homelessness services in the UK?. Project Report.[Online].ADR Wales. Available at: https://www.adruk.org/fileadmin/uploads/adruk/Documents/Data_Insights_Ageing_and_Homelessness_July_2002.pdf.
- Mackie, P. and Thomas, I. 2020. Measuring repeat homelessness. Project Report.[Online].ADR Wales. Available at: https://www.adruk.org/fileadmin/uploads/adruk/Documents/Data-Insights-Measuring-Repeat-Homelessness.pdf.
- MacKie, P. and Thomas, I. 2014. Nations apart? Experiences of single homeless people across Great Britain. Project Report.[Online].London: Crisis. Available at: http://www.crisis.org.uk/data/files/publications/NationsApart.pdf.
- Clapham, D. F. et al. 2012. Housing options and solutions for young people in 2020. Project Report.York: Joseph Rowntree Foundation.
- MacKie, P. K. et al. 2012. Assessing the impacts of proposed changes to homelessness legislation in Wales: a report to inform the review of homelessness legislation in Wales. Technical Report.
- MacKie, P. K. , Thomas, I. and Hodgson, K. 2012. Impact analysis of homelessness legislation in Wales: A report to inform the review of homelessness legislation in Wales. Project Report.[Online].Cardiff: Welsh Assembly Government. Available at: http://www.senedd.assemblywales.org/documents/s7352/Impact%20analysis%20of%20existing%20homelessness%20legislation%20in%20Wales.pdf.
- Clapham, D. F. et al. 2010. Young people and housing in 2020: identifying key drivers for change. Project Report.York: Joseph Rowntree Foundation.
Thesis
- Thomas, I. R. 2016. Network-assemblages of mediated sex: a post human study of the digital sexual practices of men who have sex with men. PhD Thesis , Cardiff University.
Research
Interests & experience
My area of interest is homelessness and housing insecurity, from a largely quantitative perspective. In the UK, quantitative data and research on the experience of homelessness is limited, when compared to other countries like the United States. My research therefore addresses this evidence gap using administrative data—data routinely generated by organisations such as charities, local authorities, and health services in the course of their everyday work. Alongside my academic research, I have extensive experience working in partnership with charities, government bodies, and other organisations to improve the collection, linkage, and use of data relating to homelessness and housing insecurity. I have collaborated with a wide range of organisations, including Shelter Cymru, Shelter Scotland, Crisis, Llamau, Newport City Council, the Welsh Government, the Royal Foundation, and the Organisation for Economic Co-operation and Development (OECD).
Methodological expertise
I have experience in the use of the following research methods:
- Data linkage.
- Sequence analysis.
- Network analysis.
- Multiple Correspondence Analysis.
- Cluster analysis.
- Latent Class Analysis.
- Longitudinal panel regression analysis.
Associated research projects
2026 – 2031: Administrative Data Research Wales (Housing theme lead), funded by ESRC.
2024 – 2026: Evaluation of Centrepoint’s Upstream youth homeless intervention (Quantitative lead), funded by Centrepoint.
2024 – 2026: Evaluation of the Rock Trust’s Upstream youth homeless intervention (Quantitative lead), funded by Rock Trust.
2022 – 2024: PHaCT Trial: Preventing Homelessness, improving health for people leaving prison: a pilot randomised controlled trial of a Critical Time intervention (Linked-data lead), funded by NIHR.
2022 – 2026: Administrative Data Research Centre Wales (Housing theme co-lead), funded by ESRC.
2018 – 2022: Administrative Data Research Centres 2016 (Quantitative lead, housing and homelessness theme), funded by ESRC.
2014: Intervention inequality? Experiences of Single Homelessness in Great Britain (Quantitative lead), funded by Crisis.
2011 - 2012: Review of homelessness legislation in Wales (Quantitative lead), funded by Welsh Government.